This invention relates to a linear actuator assembly and more particularly to a linear actuator assembly capable of speedily positioning an object with a high degree of accuracy. More concretely, this invention relates to a linear actuator assembly for use in a magnetic disk storage apparatus.
It is necessary for recent types of magnetic disk storage apparatus to perform high-speed data recording or reproduction and to perform high-density data recording or reproduction. Accordingly, an actuator assembly for positioning a magnetic head must have a capability for speedily and accurately positioning the magnetic head over a target track on a magnetic disk. To realize such a capability, it is necessary for the actuator assembly to display superior stiffness in the direction of the positioning (direction of the movement of the magnetic head), to transmit the force of a driving force generating means (e.g., a voice coil motor) through a carriage to the magnetic head without experiencing any losses, to have a reduced weight, and to be free from any likelihood of suffering deformation as a result of exposure to heat, and so forth.
However, actuator assemblies which have been provided on the basis of conventional techniques are not able to satisfy the above-described requirements with respect to stiffness, transmission of force, weight and heat deformation. An example of the prior art for linear actuators is disclosed in U.S. Pat. No. 4,144,466, in which a portion through which the force of the voice coil is transmitted to a carriage is constituted by a cylindrical voice coil and a crisscrossed carriage connected to this coil. This means that, when the force is transmitted, bending stress is caused at the connection between the cylindrical and crisscrossed portions such as to generate vibration because of the steep change in cross-sectional area created therebetween. Also, in the arrangement of this patent, the contact area between the cylindrical coil and the crisscrossed carriage is not enough to ensure that heat transfer takes place to an extent sufficient to reduce the temperature of the coil. Thus there is a risk of deformation or damage of the coil.